This work will study the mechanism whereby individual sickle cell hemoglobin molecules assembly to form ordered arrays of long, multistranded polymers. This process is of interest as a model for protein self-assembly systems, and is of importance as the cause of a seriously debilitating disease. The experiments proposed here combine the large dynamic range of laser photolysis as an initiator of the reaction with the spatial resolution of microscopic techiques. The carbon monoxide derivative of sickle cell hemoglobin will be photolyzed by a cw argon ion laser to initiate assembly in regions about 100 mum in diameter in thin layer (2 to 4 mum) samples. Assembly will be monitored by two-dimensional time-resolved simultaneous birefringence and light scattering. In studies proposed here, measurements on single domains of polymers will critically test the recently advanced dual-nucleation model for sickle cell hemoglobin gelation, and will expand upon that model. The kinetic structure of polymer domains will be studied in order to give insight into ultrastructural features of the polymers, as well as to provide information on polymer density and alignment vital for characterizing the rheological properties of sickled cells. Ligand-induced depolymerization will be studied; incomplete depolymerization of sickled cells in the lungs increases the likelihood of sickling and occlusion within the capillaries.